1. Field of the Invention
The present invention is related to annealing of surface films on low temperature substrates and, in particular, to deposition of low temperature Zirconia Based Thermal Barrier Layer which enables such annealing of surface films.
2. Discussion of Related Art
Many thermal processes for thin films, such as rapid thermal heating or pulsed laser recrystallization, require the surface film to be heated to high temperature for a period of time. Such processing can be carried out on low temperature material such as glass or plastic substrates if a thermal barrier layer is formed between the layer to be treated and the substrate.
One example of such a thermal process is the laser crystallization of amorphous silicon on a low temperature substrate. The recrystallization to form electronic grade poly silicon, requires that the silicon layer be completely melted for a period of time, typically several hundred nano seconds. The completely melted state is referred to as the full melt state (FMS) and the threshold laser power to accomplish such a melted state is referred to as the full melt threshold (FMT).
If the amorphous silicon is deposited directly on a glass substrate, the substrate may be structurally damaged by the high temperature of the liquid silicon in the full melt state. In the case of glass, diffusion of alkali or boron from the glass into the liquid silicon or other harmful diffusion or structural effects may result from the proximity heating of the glass substrate. Clearly low temperature materials such as plastic would be harmed by such a thermal process.
Consequently, a thermal barrier layer or film to isolate the heat affected layer from the substrate is advantageous. Silica is often utilized for this purpose when the substrate is glass. However the thermal conductivity of Silica are poorly matched to glass or plastic substrates and it is known that standard sputtered or CVD deposited silica results in a poor barrier for water or oxygen, and is only a marginal barrier for alkali ions and boron.
Therefore, there is a general need for a vacuum thin film, thermal barrier layer material and process demonstrating lower thermal conductivity and improved electrical and barrier properties.